We access our database with a self-written resource-adapter/translator and are using the plsqlodbc driver (v9.6.5) for MS Access.

If we limit the metadata in the VDB it works fine so far, but if we provide a huge amount of tables and views (more than 1000 with many columns and indices) the linking of a single table in MS Access takes a long time, over 5 minutes in this case.

I see related behavior upstream - but only for the first query against pg_index. In 10.1.1 as part of [TEIID-5236] Document and update GeoServer/PG JDBC compatibility - JBoss Issue Tracker that view is materialized. For 2000 tables each with an index, I see an initial query time of around 20 seconds, and subsequent timings in the 10s of milliseconds after the view is materialized. So in prior releases with a lot of tables there will be an issue.

It looks like it's a good idea to make that a managed materialization such that it will load automatically. I'll also test with even higher table counts to see if the initial load needs optimized.